// Copyright 2014 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_EXECUTION_H_
#define V8_EXECUTION_H_

#include "src/base/atomicops.h"
#include "src/globals.h"

namespace v8 {
namespace internal {

    class MicrotaskQueue;

    template <typename T>
    class Handle;

    class Execution final : public AllStatic {
    public:
        // Whether to report pending messages, or keep them pending on the isolate.
        enum class MessageHandling { kReport,
            kKeepPending };
        enum class Target { kCallable,
            kRunMicrotasks };

        // Call a function, the caller supplies a receiver and an array
        // of arguments.
        //
        // When the function called is not in strict mode, receiver is
        // converted to an object.
        //
        V8_EXPORT_PRIVATE V8_WARN_UNUSED_RESULT static MaybeHandle<Object> Call(
            Isolate* isolate, Handle<Object> callable, Handle<Object> receiver,
            int argc, Handle<Object> argv[]);

        // Construct object from function, the caller supplies an array of
        // arguments.
        V8_WARN_UNUSED_RESULT static MaybeHandle<Object> New(
            Isolate* isolate, Handle<Object> constructor, int argc,
            Handle<Object> argv[]);
        V8_WARN_UNUSED_RESULT static MaybeHandle<Object> New(
            Isolate* isolate, Handle<Object> constructor, Handle<Object> new_target,
            int argc, Handle<Object> argv[]);

        // Call a function, just like Call(), but handle don't report exceptions
        // externally.
        // The return value is either the result of calling the function (if no
        // exception occurred), or an empty handle.
        // If message_handling is MessageHandling::kReport, exceptions (except for
        // termination exceptions) will be stored in exception_out (if not a
        // nullptr).
        V8_EXPORT_PRIVATE static MaybeHandle<Object> TryCall(
            Isolate* isolate, Handle<Object> callable, Handle<Object> receiver,
            int argc, Handle<Object> argv[], MessageHandling message_handling,
            MaybeHandle<Object>* exception_out);
        // Convenience method for performing RunMicrotasks
        static MaybeHandle<Object> TryRunMicrotasks(
            Isolate* isolate, MicrotaskQueue* microtask_queue,
            MaybeHandle<Object>* exception_out);
    };

    class ExecutionAccess;
    class InterruptsScope;

    // StackGuard contains the handling of the limits that are used to limit the
    // number of nested invocations of JavaScript and the stack size used in each
    // invocation.
    class V8_EXPORT_PRIVATE StackGuard final {
    public:
        explicit StackGuard(Isolate* isolate)
            : isolate_(isolate)
        {
        }

        // Pass the address beyond which the stack should not grow.  The stack
        // is assumed to grow downwards.
        void SetStackLimit(uintptr_t limit);

        // The simulator uses a separate JS stack. Limits on the JS stack might have
        // to be adjusted in order to reflect overflows of the C stack, because we
        // cannot rely on the interleaving of frames on the simulator.
        void AdjustStackLimitForSimulator();

        // Threading support.
        char* ArchiveStackGuard(char* to);
        char* RestoreStackGuard(char* from);
        static int ArchiveSpacePerThread() { return sizeof(ThreadLocal); }
        void FreeThreadResources();
        // Sets up the default stack guard for this thread if it has not
        // already been set up.
        void InitThread(const ExecutionAccess& lock);
        // Clears the stack guard for this thread so it does not look as if
        // it has been set up.
        void ClearThread(const ExecutionAccess& lock);

#define INTERRUPT_LIST(V)                                           \
    V(TERMINATE_EXECUTION, TerminateExecution, 0)                   \
    V(GC_REQUEST, GC, 1)                                            \
    V(INSTALL_CODE, InstallCode, 2)                                 \
    V(API_INTERRUPT, ApiInterrupt, 3)                               \
    V(DEOPT_MARKED_ALLOCATION_SITES, DeoptMarkedAllocationSites, 4) \
    V(GROW_SHARED_MEMORY, GrowSharedMemory, 5)                      \
    V(LOG_WASM_CODE, LogWasmCode, 6)

#define V(NAME, Name, id)                                                      \
    inline bool Check##Name() { return CheckInterrupt(NAME); }                 \
    inline bool CheckAndClear##Name() { return CheckAndClearInterrupt(NAME); } \
    inline void Request##Name() { RequestInterrupt(NAME); }                    \
    inline void Clear##Name() { ClearInterrupt(NAME); }
        INTERRUPT_LIST(V)
#undef V

        // Flag used to set the interrupt causes.
        enum InterruptFlag {
#define V(NAME, Name, id) NAME = (1 << id),
            INTERRUPT_LIST(V)
#undef V
#define V(NAME, Name, id) NAME |
                ALL_INTERRUPTS
            = INTERRUPT_LIST(V) 0
#undef V
        };

        uintptr_t climit() { return thread_local_.climit(); }
        uintptr_t jslimit() { return thread_local_.jslimit(); }
        // This provides an asynchronous read of the stack limits for the current
        // thread.  There are no locks protecting this, but it is assumed that you
        // have the global V8 lock if you are using multiple V8 threads.
        uintptr_t real_climit()
        {
            return thread_local_.real_climit_;
        }
        uintptr_t real_jslimit()
        {
            return thread_local_.real_jslimit_;
        }
        Address address_of_jslimit()
        {
            return reinterpret_cast<Address>(&thread_local_.jslimit_);
        }
        Address address_of_real_jslimit()
        {
            return reinterpret_cast<Address>(&thread_local_.real_jslimit_);
        }

        // If the stack guard is triggered, but it is not an actual
        // stack overflow, then handle the interruption accordingly.
        Object HandleInterrupts();

    private:
        bool CheckInterrupt(InterruptFlag flag);
        void RequestInterrupt(InterruptFlag flag);
        void ClearInterrupt(InterruptFlag flag);
        bool CheckAndClearInterrupt(InterruptFlag flag);

        // You should hold the ExecutionAccess lock when calling this method.
        bool has_pending_interrupts(const ExecutionAccess& lock)
        {
            return thread_local_.interrupt_flags_ != 0;
        }

        // You should hold the ExecutionAccess lock when calling this method.
        inline void set_interrupt_limits(const ExecutionAccess& lock);

        // Reset limits to actual values. For example after handling interrupt.
        // You should hold the ExecutionAccess lock when calling this method.
        inline void reset_limits(const ExecutionAccess& lock);

        // Enable or disable interrupts.
        void EnableInterrupts();
        void DisableInterrupts();

#if V8_TARGET_ARCH_64_BIT
        static const uintptr_t kInterruptLimit = uintptr_t { 0xfffffffffffffffe };
        static const uintptr_t kIllegalLimit = uintptr_t { 0xfffffffffffffff8 };
#else
        static const uintptr_t kInterruptLimit = 0xfffffffe;
        static const uintptr_t kIllegalLimit = 0xfffffff8;
#endif

        void PushInterruptsScope(InterruptsScope* scope);
        void PopInterruptsScope();

        class ThreadLocal final {
        public:
            ThreadLocal() { Clear(); }
            // You should hold the ExecutionAccess lock when you call Initialize or
            // Clear.
            void Clear();

            // Returns true if the heap's stack limits should be set, false if not.
            bool Initialize(Isolate* isolate);

            // The stack limit is split into a JavaScript and a C++ stack limit. These
            // two are the same except when running on a simulator where the C++ and
            // JavaScript stacks are separate. Each of the two stack limits have two
            // values. The one eith the real_ prefix is the actual stack limit
            // set for the VM. The one without the real_ prefix has the same value as
            // the actual stack limit except when there is an interruption (e.g. debug
            // break or preemption) in which case it is lowered to make stack checks
            // fail. Both the generated code and the runtime system check against the
            // one without the real_ prefix.
            uintptr_t real_jslimit_; // Actual JavaScript stack limit set for the VM.
            uintptr_t real_climit_; // Actual C++ stack limit set for the VM.

            // jslimit_ and climit_ can be read without any lock.
            // Writing requires the ExecutionAccess lock.
            base::AtomicWord jslimit_;
            base::AtomicWord climit_;

            uintptr_t jslimit()
            {
                return bit_cast<uintptr_t>(base::Relaxed_Load(&jslimit_));
            }
            void set_jslimit(uintptr_t limit)
            {
                return base::Relaxed_Store(&jslimit_,
                    static_cast<base::AtomicWord>(limit));
            }
            uintptr_t climit()
            {
                return bit_cast<uintptr_t>(base::Relaxed_Load(&climit_));
            }
            void set_climit(uintptr_t limit)
            {
                return base::Relaxed_Store(&climit_,
                    static_cast<base::AtomicWord>(limit));
            }

            InterruptsScope* interrupt_scopes_;
            int interrupt_flags_;
        };

        // TODO(isolates): Technically this could be calculated directly from a
        //                 pointer to StackGuard.
        Isolate* isolate_;
        ThreadLocal thread_local_;

        friend class Isolate;
        friend class StackLimitCheck;
        friend class InterruptsScope;

        DISALLOW_COPY_AND_ASSIGN(StackGuard);
    };

} // namespace internal
} // namespace v8

#endif // V8_EXECUTION_H_
